Crosswood Reservoir

Crosswood is a small, shallow reservoir of 55 acres perched on the northern slopes of the Pentland Hills. It lies in headwaters of the River Almond at an elevation of 1012 feet above West Calder, West Lothian. It was constructed in 1868 to provide water in summer to the mills on the River Almond in compensation for the water abstracted from its springs into the North Pentlands Aqueduct to supply drinking water for Edinburgh. It has the largest catchment area, in relation to its storage capacity, of all the Lothian reservoirs. This produces rapid and marked fluctuations in water level when rain falls in the catchment.

Water Chemistry

Despite its peaty colouring, Crosswood has a neutral ph of 7.1 and a hardness of 50 mgCaCo3/litre. It is therefore good water quality with sufficient alkalinity to support most aquatic invertebrates.

Trout Feeding

No formal invertebrate survey has been carried out. Observation of hatching flies and stomach analysis of trout caught suggests that Crosswood will have the usual species common in Pentland Waters. The inflowing Crosswood burn is likely to be a source of Large Stone Fly, Yellow Sally and Needle Fly, associated with Late March Brown. The range of insect life within the reservoir includes Chironomids, Cinnamon Sedge, Claret Dun and Anglers Curse.

Their distribution will be affected by the bottom deposits. The majority of the reservoir bottom is soft mud and silt and produces large hatches of Chironomids (non-biting midges) throughout the season. The more solid bottoms of rocks and boulders, around the edges, produce Cinnamon Sedge, Claret Dun, freshwater shrimp and hog louse. In addition Crosswood has the usual populations of worms, snails and minnows. Terrestrial insects include Heather Fly and Daddy Long Legs in season.

Wild Trout Population

Spawning of reservoir trout is restricted to the bottom kilometre of the Crosswood Burn, below an impassable waterfall. Crosswood Burn produces plenty of young trout, which stay there for 1, 2 or 3 years before migrating down to the reservoir. 2 year olds will enter the reservoir at a mean size of 3.8 inches. Some will stay in the burn for 3 years attaining a mean length of 8.7 inches.